3  Optical studies of ion–molecule reactions

Frost, Michael J.

doi:10.1039/b313663a

Cited by 2 publications

(4 citation statements)

References 258 publications

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“…The updated I and A data are listed in Supporting Information Table S, for their references, see Refs. [].…”

Section: The Performance Of Valence‐pair Equilibrationmentioning

confidence: 99%

“…The photoelectron spectra of the halogen acids, HX, are resolved into the 2 Π and 2 Σ + bands, and I 0 ( 2 Π ) corresponds to removing an electron from a lone‐pair MO, while I b ( 2 Σ + ) refers to the σ‐bond . The anions HX − are unstable, but their A 0, v (HX) are obtained from the resonance peaks in dissociative electron attachment experiments and at advanced levels of theory . The VPA is well equalized to about δ α VP (HX) ≈ 2 to 8%, which is about an order of magnitude smaller than δμ op (HX) ≈ 20 to 34%.…”

Section: The Performance Of Valence‐pair Equilibrationmentioning

confidence: 99%

“…We investigate molecules with up to four equivalent bonds, such as CO 2 , H 2 O, CH 3 , SiH 3 , NH 3 , CX 4 (X = H, F, Cl, Br), SiH 4 and molecules characterized by non‐equivalent bonds, for example , HCN, COS, CH 3 I, C 2 H 2 , C 2 H 4 , C 2 H 6 , and H 2 C = O (Table ) and Supporting Information (Table S1). Several polyatomic electron affinities have been revised and differ significantly from the values used earlier . Due to some exaggeratedly negative A 0, v values in Refs.…”

Section: The Performance Of Valence‐pair Equilibrationmentioning

confidence: 99%

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Eliminating symmetry problems in electronegativity equalization and correcting self‐interaction errors in conceptual DFT

Szentpály

2018

J Comput Chem

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The chemical potential is by definition constant in molecules, and electronic charge is in principle equilibrated by bonding. Does electronegativity offer the best scale to unify these principles? According to conceptual density functional theory (c-DFT), the electronegativity equalization (ENE) and chemical potential equalization (CPE) principles seem rigorous and identical. However, the operational formulations of CPE and ENE fail to validate this claim, and frequently dramatic deviations from equalization are reported. We here eliminate the deviations to a very large extent. The problems originate from (i) c-DFT's exclusive reference to ground states and violations of the Wigner-Witmer symmetry constraints for bonding, (ii) electron self-interaction and delocalization errors. The problems are solved, and much more accurate ENE and bond polarities are obtained by replacing the ground-state electronegativity (χ ) by the valence-state electronegativity (χ ) and its generalization, the valence-pair-affinity (VPA, α ). The VPA is a charge dependent pair-sharing potential connected to Ruedenberg's bond theory that emphasizes the role of electron pair-density. The performances of the valence-pair equilibration (VPEq) and c-DFT's operational CPE are compared for 89 molecules with very diverse bond characters, including the "exotic" dimers Be , Mg , B , C , and Mn . The accuracy of VPEq is about 9 times better than that of operational CPE. Without requiring ad hoc calibrations, the VPEq bond polarities agree very well with results of state-of-the-art population analyses, and charges derived from vibrational spectra. A paradigm shift emphasizing valence states seems in order for c-DFT. Electronegativity and the chemical potential should be regarded as separate properties. Copyright © 2018 Wiley Periodicals, Inc.

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“…The updated I and A data are listed in Supporting Information Table S, for their references, see Refs. [].…”

Section: The Performance Of Valence‐pair Equilibrationmentioning

confidence: 99%

Section: The Performance Of Valence‐pair Equilibrationmentioning

confidence: 99%

Section: The Performance Of Valence‐pair Equilibrationmentioning

confidence: 99%

See 1 more Smart Citation

Eliminating symmetry problems in electronegativity equalization and correcting self‐interaction errors in conceptual DFT

Szentpály

2018

J Comput Chem

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“…A detailed understanding of electron interactions with small molecular systems is also of importance in the development of theory. In this regard, the interaction of electrons with hydrogen halide molecules has received attention for many years 1–6. This article is concerned with the dissociative attachment (DA) of electrons to (HF) 2 and (HCl) 2 dimers, and in particular with the barrier height for reaction (1)* in these two systems.…”

Section: Introductionmentioning

confidence: 99%

Potential energy barriers for dissociative attachment to HF.HF and HCl.HCl: Ab initio study

Rauk

2003

Int J of Quantum Chemistry

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has been investigated by theoretical calculations at MP2 and CCSD(T) levels with large basis sets. Transition structures (TSs) for the loss of an H atom and formation of the FHF Ϫ and ClHCl Ϫ anions were located by analytic methods. Initial electron attachment to HF.HF dimer occurs without activation and yields a dipole-bound anion state (DBS) as shown previously. Reaction (1) is endothermic by 65.8 kJ/mol at the CCSD(T)/augcc-pVDZ level. An intermediate ion-induced dipole complex between H ⅐ and FHF Ϫ is reached from the DBS over a potential barrier of 66.6 kJ/mol. Analysis of the charge distribution as a function of the distance to the departing H ⅐ reveals that the diffuse DBS collapses to a much more compact valence configuration prior to the TS being reached. In the valence configuration, the electron occupies the * orbital of the terminal HOF bond. DA to HCl.HCl differs from the fluorine case in several important respects. HCl.HCl does not form a DBS. Rather, electron attachment occurs by direct insertion into the * orbital of the terminal HOCl bond with an activation energy of 20.3 kJ/mol. As in the fluorine case, electron capture occurs before the TS. The electron density collapses to a valence configuration when the HOCl bond is stretched to about 1.45 Å, intermediate between that in the neutral dimer, 1.28 Å, and in the TS to DA, 1.57 Å. A "T-shaped" ion-induced dipole complex, bound by about 2 kJ/mol, lies between the TS and the separated H atom and ClHCl Ϫ anion products. With respect to DA, the chlorine system is intermediate between the fluorine system and the previously reported bromine system. The latter was found to undergo DA with a 0.0-kJ/mol barrier.

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3 Optical studies of ion–molecule reactions

Cited by 2 publications

References 258 publications

Eliminating symmetry problems in electronegativity equalization and correcting self‐interaction errors in conceptual DFT

Eliminating symmetry problems in electronegativity equalization and correcting self‐interaction errors in conceptual DFT

Potential energy barriers for dissociative attachment to HF.HF and HCl.HCl: Ab initio study

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